JavaScript is a scripting language often used for client-side web development. Although best known for its use in websites (as client-side JavaScript), JavaScript is also used to enable scripting access to objects embedded in other applications. The primary use of JavaScript is to write functions that are embedded in or included from HTML pages and interact with the Document Object Model (DOM) of the page. Other scripting languages include VBScript and ECMAScript. For example, scripting languages may be used to open or “pop up” a new window with programmatic control over the size, position and look of the new window or to validate web form input values before they are submitted to a server.
JSON, or JavaScript Object Notation, is a general-purpose data interchange format that is defined as a subset of JavaScript. JSON is a text-based, human-readable format for representing simple data structures and associative arrays (called objects). The JSON format is often used for transmitting structured data over a network connection in a process called serialization. JSON is primarily used in Ajax web application programming, where it serves as an alternative to the use of the XML format. However, JSON requires that the fields or properties of an object are included with each object. The following is an example of a contact object in JSON format:
{ “contact”: { ″name″: ″Joe Smith″,  ″email″: “joe.smith@live.com”,  ″IsFavorite″: true,  Etc... }}}
Ajax (asynchronous JavaScript and XML), or AJAX, is a group of interrelated web development techniques used for creating interactive web applications or rich Internet applications. With Ajax, web applications can retrieve data from the server asynchronously in the background without interfering with the display and behavior of the existing page. Data is retrieved using the XMLHttpRequest object or through the use of Remote Scripting in browsers that do not support it. Despite the name, the use of JavaScript, XML, or asynchrony is not required.